Copper (i) compounds useful as deposition precursors of copper thin films

ABSTRACT

Copper (I) amidinate precursors for forming copper thin films in the manufacture of semiconductor devices, and a method of depositing the copper (I) amidinate precursors on substrates using chemical vapor deposition or atomic layer deposition processes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/119,362 filed May 12, 2008 in the name of Chongying Xu, et al.(issued May 12, 2009 as U.S. Pat. No. 7,531,031), which is acontinuation of U.S. patent application Ser. No. 11/626,363 filed onJan. 23, 2007 in the name of Chongying Xu, et al. (issued May 13, 2008as U.S. Pat. No. 7,371,880), which in turn is a continuation of U.S.patent application Ser. No. 11/149,045 filed on Jun. 9, 2005 in the nameof Chongying Xu, et al. (issued Jul. 10, 2007 as U.S. Pat. No.7,241,912), which is also a continuation of U.S. patent application Ser.No. 10/869,532 filed on Jun. 16, 2004 in the name of Chongying Xu, etal. (issued Jan. 23, 2007 as U.S. Pat. No. 7,166,732). The disclosuresof all of said prior applications are hereby incorporated herein byreference, in their respective entireties, for all purposes.

FIELD OF THE INVENTION

The present invention relates generally to novel copper (I) amidinatesand their synthesis, and to a method for production of copper circuitsin microelectronic device structures using the novel copper precursors.

DESCRIPTION OF THE RELATED ART

As a result of its low resistivity, low contact resistance, and abilityto enhance device performance through the reduction of RC time delays,copper has emerged as a preferred metal for metallization of very largescale integrated (VLSI) devices. Copper metallization has been adoptedby many semiconductor device manufacturers for production ofmicroelectronic chips, thin-film recording heads and packagingcomponents.

Chemical vapor deposition (CVD) of copper provides uniform coverage forthe metallization. Atomic layer deposition (ALD), which is a modifiedCVD process, also provides uniform coverage which is critical for copperseed layers. Liquid CVD precursors and/or solid precursors dissolvedinto solvents enable direct injection and/or the liquid delivery ofprecursors into a CVD or ALD vaporizer unit. The accurate and precisedelivery rate can be obtained through volumetric metering to achievereproducibility during CVD or ALD metallization of a VLSI device.

Many fluorine and/or oxygen-containing copper CVD precursors arecommercially available, including (hfac)Cu(MHY), (hfac)Cu(3-hexyne),(hfac)Cu(DMCOD) and (hfac)Cu(VTMS), whereinhfac=1,1,1,5,5,5-hexafluoroacetylacetonato, MHY=2-methyl-1-hexen-3-yne,DMCOD=dimethylcyclooctadiene, and VTMS=vinyltrimethylsilane.

Copper metallization in integrated circuit manufacture typicallyutilizes a barrier layer between the copper layer and the underlyingstructure in order to prevent detrimental effects that may be caused bythe interaction of a copper layer with other portions of the integratedcircuit. A wide range of barrier materials is conventionally utilized,including materials comprising metals, metal nitrides, metal silicides,and metal silicon nitrides. Exemplary barrier materials include titaniumnitride, titanium silicide, tantalum nitride, tantalum silicide,tantalum silicon nitrides, niobium nitrides, niobium silicon nitrides,tungsten nitride, and tungsten silicide. In instances where (hfac)CuLtype precursors are used for copper metallization, interfacial layersare formed between the barrier layer and the copper layer, which causethe metallization to have poor adhesion and high contact resistivity.

The deficiencies of inferior adhesion and excessively high contactresistivity incident to formation of oxygen- and/or fluorine-containinginterfacial layers when using (hfac)CuL copper precursors has beenattributed to the hfac ligand, which contains both oxygen and fluorine.To overcome such deficiencies, it would be a significant advance in theart to provide copper precursors having a reduced oxy/fluoro content. Itwould be particularly advantageous to provide copper precursors of anoxygen-free character.

It is accordingly an object of the present invention to provide newanoxic (oxygen-free and fluorine-free) copper precursors andformulations, as well as methods of forming copper in the manufacturingof integrated circuits and other microelectronic device structures usingsuch precursors and formulations.

SUMMARY OF THE INVENTION

The present invention relates generally to copper (I) amidinatecompounds, which are advantageously of an oxygen-free and fluorine-freecharacter, useful as source reagents for forming copper on substrateswith improved adhesion, and to methods of using such copper (I)amidinate compounds.

The present invention in one aspect relates to a copper precursorcompound of the formula:

wherein:R¹ and R² may be the same as or different from one another and each isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silyl groups(e.g., —SiR₃, wherein R is independently selected from the groupconsisting of C₁-C₆ alkyl);R³ is selected from the group consisting of H, C₁-C₆ alkyl, C₃-C₇cycloalkyl, aryl, hydrocarbyl derivatives of silyl groups and NR⁴R⁵,where R⁴ and R⁵ may be the same as or different from one another and isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silyl groups;with the proviso that when R¹ and R² are isopropyl groups, R³ is not amethyl group.

In another aspect, the present invention relates to a copper precursorformulation, comprising:

(a) a copper precursor compound of the formula:

wherein:R¹ and R² may be the same as or different from one another and each isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silyl groups;R³ is selected from the group consisting of H, C₁-C₆ alkyl, C₃-C₇cycloalkyl, aryl, hydrocarbyl derivatives of silyl groups and NR⁴R⁵,where R⁴ and R⁵ may be the same as or different from one another and isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silyl groups;(b) a solvent composition for the precursor compound.

In yet another aspect, the present invention relates to a method ofdepositing copper on a substrate, comprising volatilizing a copperprecursor of the formula:

wherein:R¹ and R² may be the same as or different from one another and each isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silyl groups;R³ is selected from the group consisting of H, C₁-C₆ alkyl, C₃-C₇cycloalkyl, aryl, hydrocarbyl derivatives of silyl groups and NR⁴R⁵,where R⁴ and R⁵ may be the same as or different from one another and isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silyl groups;with the proviso that when R¹ and R² are isopropyl groups, R³ is not amethyl group, to form a precursor vapor and contacting the precursorvapor with the substrate under elevated temperature vapor decompositionconditions to deposit copper on the substrate.

Other aspects, features and embodiments of the invention will be morefully apparent from the ensuing disclosure and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an ¹H-NMR plot for copper (I)2-isopropyl-1,3-diisopropylamidinate.

FIG. 2 is a simultaneous thermal analysis (STA)/differential scanningcalorimetry (DSC) plot for copper (I)2-isopropyl-1,3-diisopropylamidinate.

FIG. 3 is an ORTEP structure for copper (I)2-isopropyl-1,3-diisopropylamidinate.

FIG. 4 is an STA/DSC plot for copper (I)2-dimethylamino-1,3-diisopropylamidinate.

FIG. 5 is an ORTEP structure for copper (I)2-dimethylamino-1,3-diisopropylamidinate.

DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS THEREOF

The present invention relates to novel copper (I) amidinate precursorsfor the CVD or ALD formation of copper thin films on substrates, and tocorresponding processes for using such precursors.

Amidinates are bulky monoanionic ligands which have the basic chemicalstructure:

In one aspect, the invention provides a compound of the formula

wherein:R¹ and R² may be the same as or different from one another and each isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl aryl, and hydrocarbyl derivatives of silyl groups(e.g., —SiR₃, wherein R is independently selected from the groupconsisting of C₁-C₆ alkyl);R³ is selected from the group consisting of H, C₁-C₆ alkyl, C₃-C₇cycloalkyl, aryl, hydrocarbyl derivatives of silyl groups and NR⁴R⁵,where R⁴ and R⁵ may be the same as or different from one another and isindependently selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silyl groups;with the proviso that when R¹ and R² are isopropyl groups, R³ is not amethyl group.

The compounds of formula (1) are usefully employed for forming copperthin films by CVD or ALD processes, utilizing process conditions,including appertaining temperatures, pressures, concentrations, flowrates and CVD techniques, as readily determinable within the skill ofthe art for a given application.

Preferred compounds of formula (1) include copper (I)2-isopropyl-1,3-diisopropylamidinate:

and copper (I) 2-dimethylamino-1,3-diisopropylamidinate:

Compounds of formula (1) are readily synthesized according to thefollowing equations (2) and (3):

as hereinafter more fully described in the examples herein.

In CVD or ALD usage, the copper (I) precursors of the invention arevolatilized to form a precursor vapor that is then contacted with asubstrate under elevated temperature vapor decomposition conditions todeposit copper on the substrate.

Copper (I) 2-isopropyl-1,3-diisopropylamidinate and copper (I)2-dimethylamino-1,3-diisopropylamidinate are both volatile and thermallystable, and are usefully employed as copper CVD or ALD precursors underreducing ambient deposition conditions in the CVD or ALD reactor. Thesolid precursor can be dissolved in organic solvents, and liquiddelivery can be used to meter the solution into a vaporizer fortransport to the reactor.

More specifically, and by way of example, the copper (I) amidinateprecursor compositions of the present invention may be used during theformation of copper interconnect lines in semiconductor integratedcircuitry, thin-film circuitry, thin-film packaging components andthin-film recording head coils. To form such integrated circuitry orthin-film circuitry, a semiconductor substrate may be utilized having anumber of dielectric and conductive layers (multilayers) formed onand/or within the substrate. The semiconductor substrate may include abare substrate or any number of constituent layers formed on a baresubstrate.

In the broad practice of the present invention, a copper-containinglayer may be formed on a semiconductor substrate using the copper (I)amidinate precursor, for use in a first, second, third, or moremetallization layer. Such copper layers typically are used in circuitlocations requiring low resistivity, high performance and/or high speedcircuit paths. As discussed in the background section hereof, a barrierlayer may be deposited or otherwise formed on the substrate before acopper layer is formed on a semiconductor substrate.

Using the copper precursor compositions described herein, copper maythen be deposited on the wafer using a CVD or ALD system, such systemsbeing well known in the semiconductor fabrication art. Further, water,water-generating compounds, or other adjuvants to the precursorformulation may be mixed with the copper precursor upstream of, orwithin, the CVD or ALD tool. Similarly, reducing agents may be utilizedin an analogous fashion.

As a further variation, when copper alloy compositions are to bedeposited on the substrate, the copper precursor formulation may containor be mixed with other metal source reagent materials, or such otherreagent materials may be separately vaporized and introduced to thedeposition chamber.

The compositions of the present invention may be delivered to a CVD orALD reactor in a variety of ways. For example, a liquid delivery systemmay be utilized. Alternatively, a combined liquid delivery and flashvaporization process unit may be employed, such as the LDS300 liquiddelivery and vaporizer unit (commercially available from AdvancedTechnology Materials, Inc., Danbury, Conn.), to enable low volatilitymaterials to be volumetrically delivered, leading to reproducibletransport and deposition without thermal decomposition of the precursor.Both of these considerations of reproducible transport and depositionwithout thermal decomposition are essential for providing a commerciallyacceptable copper CVD or ALD process.

In liquid delivery formulations, copper precursors that are liquids maybe used in neat liquid form, or liquid or solid copper precursors may beemployed in solvent formulations containing same. Thus, copper precursorformulations of the invention may include solvent component(s) ofsuitable character as may be desirable and advantageous in a given enduse application to form copper on a substrate. Suitable solvents may forexample include alkane solvents, e.g., hexane, heptane, octane, pentane,or aryl solvents such as benzene or toluene, amines and amides. Theutility of specific solvent compositions for particular copperprecursors may be readily empirically determined, to select anappropriate single component or multiple component solvent medium forthe liquid delivery vaporization and transport of the specific copperprecursor employed.

In another embodiment of the invention, a solid delivery system may beutilized, for example, using the ProE-Vap solid delivery and vaporizerunit (commercially available from Advanced Technology Materials, Inc.,Danbury, Conn.).

A wide variety of CVD or ALD process conditions may be utilized with theprecursor compositions of the present invention. Generalized processconditions may include substrate temperature ranges of 150-400° C.;pressure ranges of 0.05−5 Ton; and carrier gas flows of helium,hydrogen, nitrogen, or argon at 25−750 sccm at a temperatureapproximately the same as the vaporizer of 50 to 120° C.

The deposition of copper thin films with useful electrical properties(low resistivity) and good adhesion to the barrier layer (e.g., formedof TiN or TaN), are also achieved by the process and precursors of thepresent invention. The conformality of the deposited film is practicallyachievable through CVD or ALD techniques that preferably provide apathway to the achievement of “full-fill” copper metallization. Theliquid delivery approach of the present invention, including “flash”vaporization and the use of copper precursor chemistry as hereindisclosed, enable next-generation device geometries and dimensions to beattained, e.g., a conformal vertical interconnect of 65 nanometerlinewidths. The conformal deposition of interconnects of these criticaldimensions cannot be realized by currently available physical depositionmethods. Thus, the approach of the present invention affords a viablepathway to future generation devices, and embodies a substantial advancein the art.

The features and advantages of the invention are more fully shown by thefollowing illustrative and non-limiting examples.

Example 1 Synthesis of copper (I) 2-isopropyl-1,3-diisopropylamidinate

The reaction was carried out under a steady flow of nitrogen. A Schlenkflask was charged with 6.3 g of 1,3-diisopropylcarbodiimide((CH₃)₂CHN═C═NCH(CH₃), 49.9 mmol) and 50 mL dry ether and placed in anice bath. Then, 32 mL of isopropyllithium (1.6M in ether, 51.2 mmol) wasadded dropwise to the magnetically stirred mixture at about 0° C. Afterthe addition was complete, the mixture was stirred at room temperaturefor two additional hours. The mixture was transferred to another flaskcontaining 6 g of CuCl (60.6 mmol) suspended in 50 mL ether. Thismixture was stirred at room temperature overnight and then stripped todryness. The solid residue was extracted with pentane (3×50 mL). Afterextraction, the pentane filtrate was concentrated to slightly cloudy.The saturated solution was placed in a freezer at −39° C., andcrystalline product was obtained in a yield of about 60%.

FIG. 1 shows the ¹H NMR (C₆D₆) for copper (I)2-isopropyl-1,3-diisopropylamidinate, having the following peaks: δ 1.20(d, 6H, (CH₃)₂CH—C), 1.23 (br, 12H, (CH₃)₂CH—N), 3.20 (hept, 1H, CH),3.45 (br, 1H, CH), 3.95 (br, 1H, CH).

FIG. 2 shows the STA/DSC plot for copper (I)2-isopropyl-1,3-diisopropylamidinate. The melting peak is about 160° C.and the residue is about 19%.

FIG. 3 is the ORTEP structure for copper (I)2-isopropyl-1,3-diisopropylamidinate, showing the dimeric structure ofthe compound and 30% probability thermal ellipsoids.

Example 2 Synthesis of copper (I)2-dimethylamino-1,3-diisopropylamidinate

Neat 1,3-diisopropylcarbodiimide (12.37 g, 98 mmol, 15.2 mL) was slowlyadded to a solution of LiNMe₂ (5 g, 98 mmol) in 125 mL of THF. Some heatgeneration was observed. The reaction mixture was stirred for 1 hour.Thereafter, 9.7 g of solid CuCl (98 mmol) was added to the reactionmixture in a dry box. The resulting greenish suspension was stirredovernight and all volatiles were removed in vacuum. The residue waswashed in 150 mL of hexane. Filtrate was concentrated in vacuum andplaced in a refrigerator whereby neat crystals grew overnight. Theoverall yield was 60% and the melting point of the crystals was 108° C.¹H NMR (C₆D₆): δ 3.42 (septet, 1H, (H—H)=6 Hz, CH(CH₃)₂), 2.55 (singlet,3H, N(CH₃)₂), 1.30 (doublet, 6H, J(H—H)=6 Hz, CH(CH₃)₂). ¹³C NMR (C₆D₆):δ 171.95 (Me₂NC(N(iPr))₂), 48.61 (CH(CH₃)₂), 41.29 (N(CH₃)₂), 27.98(CH(CH₃)₂).

FIG. 4 shows the STA/DSC plot for copper (I)2-dimethylamino-1,3-diisopropylamidinate, which is volatile with thetransport temperature below 230° C., and having a residual mass below5%.

FIG. 5 is the ORTEP structure for copper (I)2-dimethylamino-1,3-diisopropylamidinate, showing the dimeric structureof the compound in the solid state. A relatively short Cu—Cu distance of2.4152(17) Å may indicate a weak metal-metal interaction. The averageCu—N distance is 1.875(3) Å, which is quite similar to that observed inanalogous compounds.

While the invention has been described herein with reference to variousspecific embodiments, it will be appreciated that the invention is notthus limited, and extends to and encompasses various other modificationsand embodiments, as will be appreciated by those ordinarily skilled inthe art. Accordingly, the invention is intended to be broadly construedand interpreted, in accordance with the ensuing claims.

1. A method of making a VLSI device, comprising forming a VLSI devicestructure requiring metallization, and metallizing the VLSI devicestructure with copper interconnect lines, wherein said metallizingcomprises vapor deposition of copper, utilizing a copper precursorcomposition comprising a copper precursor of the formula:

wherein: R¹ and R² may be the same as or different from one another andeach is independently selected from the group consisting of H, C₁-C₆alkyl, C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silylgroups; R³ is selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, hydrocarbyl derivatives of silyl groups andNR⁴R⁵, where R⁴ and R⁵ may be the same as or different from one anotherand is independently selected from the group consisting of H, C₁-C₆alkyl, C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silylgroups.
 2. The method of claim 1, wherein said vapor deposition ofcopper comprises full fill copper metallization.
 3. The method of claim1, wherein said vapor deposition of copper comprises chemical vapordeposition or atomic layer deposition.
 4. The method of claim 1, whereinsaid copper interconnect lines comprise a nanometer-scale linewidth. 5.The method of claim 4, wherein said copper interconnect lines comprise aconformal vertical interconnect.
 6. The method of claim 4, wherein saidcopper interconnect lines comprise 65 nanometer linewidth coppermetallization.
 7. The method of claim 1, wherein said copper precursorcomprises copper (I) 2-isopropyl-1,3-diisopropylamidinate.
 8. The methodof claim 1, wherein said copper precursor comprises copper (I)2-dimethylamine-1,3-diisopropylamidinate.
 9. The method of claim 1,wherein said copper precursor composition comprises an adjuvant selectedfrom among water, water-generating compounds and reducing agents. 10.The method of claim 1, wherein said copper precursor compositioncomprises a solvent medium.
 11. The method of claim 10, wherein saidsolvent medium comprises an alkane solvent.
 12. The method of claim 10,wherein said solvent medium comprises an aryl solvent.
 13. The method ofclaim 10, wherein said solvent medium comprises a solvent selected fromthe group consisting of hexane, heptane, octane, pentane, benzene,toluene, amines and amides.
 14. The method of claim 1, wherein said VLSIdevice structure is selected from the group consisting of semiconductorintegrated circuitry, thin-film circuitry, thin-film packagingcomponents and thin-film recording head coils.
 15. The method of claim1, wherein said VLSI device structure comprises dielectric andconductive layers formed on and/or within a substrate.
 16. The method ofclaim 1, wherein said vapor deposition of copper comprises depositingcopper on a barrier layer of the VLSI device structure.
 17. The methodof claim 16, wherein said barrier layer comprises TiN or TaN.
 18. A VLSIdevice, manufactured by a process including metallization of a VLSIdevice structure with copper interconnect lines by vapor deposition ofcopper, utilizing a copper precursor composition comprising a copperprecursor of the formula:

wherein: R¹ and R² may be the same as or different from one another andeach is independently selected from the group consisting of H, C₁-C₆alkyl, C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silylgroups; R³ is selected from the group consisting of H, C₁-C₆ alkyl,C₃-C₇ cycloalkyl, aryl, hydrocarbyl derivatives of silyl groups andNR⁴R⁵, where R⁴ and R⁵ may be the same as or different from one anotherand is independently selected from the group consisting of H, C₁-C₆alkyl, C₃-C₇ cycloalkyl, aryl, and hydrocarbyl derivatives of silylgroups.
 19. The VLSI device of claim 18, wherein said copperinterconnect lines include conformal vertical interconnects withnanometer-scale linewidths.
 20. The VLSI device of claim 19, whereinsaid nanometer-scale linewidths comprise 65 nanometer linewidths.